The invention relates to an angle adjusting mechanism that holds two members at a desired relative angular position.
A boom type microphone stand, which is shown in FIG. 6 hereof, provides one application or use for the invention. As shown in FIG. 6, the microphone stand comprises a main stand S, an arm A on which a microphone is installed, and a boom 80 which connects the stand S and the arm A to be freely adjustable in terms of their relative rotation angle.
As is shown in FIGS. 7 and 8, a conventional angle adjusting mechanism for the boom 80 comprises a fixed member 81 that is installed on the main stand S and a movable member 82 that is installed on the arm A. Two friction plates 83 on opposite sides of the member 82 are compressively tightened by tightening the fixed member 81 and spaced apart parallel, upstanding support walls 86 by means of a cooperating tightening bolt 84 and a nut 85, thereby fixing the tilt angle of the movable member 82 A metal washer 87 is disposed beneath the nut 85.
However, this conventional mechanism suffers bending from the upper side 88 of the support walls 86, at the end of the fixed member 81 when the tightening bolt 84 and the nut 85 are tightened. When the friction plates 83 are made of a substance like rubber, etc. having compressibility, what is then the upper side of the friction plate 83A is more strongly compressed than the lower side of that plate, as shown in FIG. 9. The uneven compression of the friction plate 83A causes a one-sided tightening of the movable member 82 and causes asymmetrical wearing of the friction plate 83A, which speeds up the aging process of the rubber material of the plate.
A friction plate made of a non-compressible material, like a plastic, is shown in FIG. 10, which also illustrates a conventional design. When a tightening force is applied to the top part 89 of both friction plates 83B, the tightening force is applied partially and insufficiently against the movable part 82. Much wearing of the top part 89 occurs, because of the eccentric load that is applied to the friction plates 83B. As the wearing of the top part 89 becomes greater, a greater tightening force on the nut 85 will be required to obtain the same amount of tightening force on the friction plates 83B. This decreases the durability of the friction plates and of the tightening nut. At the same time, cracks and ruptures may develop in the fixed member.
When the arm A is long or its weight is great, further, a larger tightening force is required to prevent the arm A from sagging down. This requires that the angle adjusting mechanism itself be made larger in size, which creates problems not only in terms of its over large outside appearance but also in terms of its functional ability.